It all depends on the specific situation. If you happen to be using the Mixlib::ShellOut class, the output of the run_command can be read with the #stdout method. This class also offers a :input option as part of the initializer that should pass any input into STDIN when running a command (http://www.rubydoc.info/github/opscode/mixlib-shellout/Mixlib/ShellOut#input-instance_method). I recommend checking out the Mixlib::ShellOut class if you haven’t already.